Need Flip Flops for Flat Feet

Olukai
Reef
These 2 brands, are great.
Very well made.
They both have arch support.
BOTH are what the young/old/teens/kids/Surfers/hip people wear, here.

Look it up online. ie: "how are the arch supports on Reef slippers." "How are the arch supports on Olukai slippers..."
Both are very comfortable.
In my State, "slippers" as we call them (not flip flops), are what everyone wears daily. And they wear slippers for doing everything, from going to school to sports to skateboarding to going to the beach. These slippers handle everything and are very sturdy. And well worth the price.
In fact, I STILL have my Reef slippers... that I had since college. And it is still good and new looking.
In fact we even have these slippers in our house!

What about Crocs? Would he wear them? They will support his feet better than flip flops...

Keen and Teva have brought up their styles over the years. particularly, Teva, which used to be a sandal/flip flop that river rafters wore..
Also, you can get a good flip flop by many shoe designers, you ll have to pay more than you would the standard rubber ones, but they are out there..
good luck

Whole Earth Provisions
There is one in Houston . Here is a 20% 0ff good through this weekend on any shoes.

The students at UT purchase their flip flops from there.
You know, Columbia ,Teva...

http://blogs.wholeearthprovision.com/products/2014/02/tak...

Try Lands End and LL Bean, too. They will certainly be cute enough for him.